The present invention relates to the field of exhaust ducts and exhaust stacks for fans and the like.
Many exhaust gases are noxious. Accordingly, it is desirable, when constructing exhaust systems, for buildings or the like, to attempt to ensure that exhaust gases do not persist at low altitudes, but instead travel upwardly, into the atmosphere.
Tall exhaust stacks can be highly effective in this regard, even in the context of exhaust gases exiting therefrom at relatively low velocities. However, tall exhaust stacks are relatively costly and difficult to construct. Moreover, same are unsightly, and can also exceed height restrictions imposed under zoning by-laws.
Accordingly, it has been attempted to approximate the performance of tall stacks by the use of upblast fans, which exhaust gases at high velocity through relatively short stacks of conventional construction. However, such structures have proven deficient in terms of their ability to propel exhaust gases upwardly into the atmosphere. It has been found, for example, that atmospheric currents can create eddies adjacent to building rooflines, which can entrain gases exhausted from conventional short stacks even when exiting at relatively high velocities.
One class of upblast fan which can be relatively effective in the propulsion of exhaust gases upwardly into the atmosphere is characterized by a radial fan which exhausts into a bifurcated nozzle defining opposed flow chambers, each being substantially arcuate in horizontal cross-section and collectively tapering upwardly to an outlet, with a passive zone chamber defined between the chambers that is open to the atmosphere. The structures described in U.S. Pat. No. 4,806,076 (Andrews), issued Feb. 21, 1989; U.S. Pat. No. 5,439,349 (Kupferberg), issued Aug. 8, 1995; and U.S. Pat. No. 6,112,850 (Secrest et al.), issued Sep. 5, 2000, are all exemplary of this class.
It is an object of the present invention to provide a novel nozzle for an upblast fan enables the propulsion of exhaust gases upwardly into the atmosphere.
According to one aspect of the invention, an exhaust gas nozzle comprises a vertically extending duct member forming an exhaust passage that extends from an open bottom end to an open top end of the duct member. A centrally disposed, vertically extending longitudinal axis extends between the first and second ends. The duct member is formed by a duct wall that extends peripherally around the longitudinal axis and that has at least two longitudinally extending, bent wall portions distributed substantially evenly about the periphery of the duct member. These bent wall portions gradually and increasingly pinch the passage in the direction of the second end by bending and projecting radially inwardly towards the longitudinal axis as seen from the top end of the duct member.
In a preferred embodiment, the gas nozzle includes an annular, open-ended cap connected to the duct member and disposed about the exterior of and in spaced, substantially coaxial relation to the second end of the duct member. The cap has a cap inlet located in the region of the second end and outside the duct member and a cap outlet located above the second end.
According to another aspect of the invention, an exhaust gas nozzle comprises a duct member forming a single exhaust passage that extends from an open, first end to an open second end of the duct member. A centrally disposed longitudinal axis extends between the first and second ends. The duct member is formed by a duct wall having at least two longitudinally extending bent wall portions that are distributed substantially evenly about the periphery of the duct member, which extends about the longitudinal axis. Each bent wall portion projects inwardly towards the longitudinal axis as seen in transverse planes in the region of the second end whereby the bent wall portions gradually and increasingly pinch the single passage in the direction of the second end. An annular cap is connected to the duct member and is disposed about the exterior of and in spaced, substantially coaxial relation to the second end of the duct member. The cap has a cap inlet located between the first and second ends and outside the duct member. A cap outlet is located outwardly from the second end in the direction of the longitudinal axis.
In one preferred embodiment of this nozzle, there are only two of the bent wall portions which are located diametrically opposite one another. In other versions of the nozzle, there can be three or four bent wall portions distributed about the periphery of the duct member.
Other advantages, features and characteristics will become more apparent upon consideration of the following detailed description with reference to the accompanying drawings, the latter being briefly described hereinbelow.